What Illinois requires for emissions testing
Illinois requires an emissions test every two years for most vehicles, and every year for vehicles in Cook County (which includes Chicago). You must pass this test to renew your vehicle registration. The test measures what comes out of your tailpipe — specifically nitrogen oxides, particulate matter, and hydrocarbons — to make sure your vehicle meets state air quality standards.
The state runs this program through the Illinois Environmental Protection Agency (IEPA), but you do not go to a government office to take the test. Instead, you visit a private testing station that the IEPA has certified. These stations are repair shops, quick-lube facilities, and dedicated testing centers scattered across the state.
Your vehicle must be registered in Illinois to be tested here. If you just moved to the state or recently bought a car, you will need your Illinois registration before you can schedule a test. The test itself takes about 10 to 15 minutes and costs between $25 and $35, depending on the station.
Key Takeaways
- Illinois requires an emissions test every two years statewide, and every year in Cook County, to renew your vehicle registration.
- You take the test at a private certified station, not a government office, and the test costs $25 to $35.
- The test measures tailpipe emissions and takes about 10 to 15 minutes.
- If you fail, you have 30 days to fix the problem and retest at no additional charge at the same station.
- You can find certified testing stations through the IEPA website or by calling 1-800-253-5747.
Finding a certified testing station near you
The IEPA maintains a searchable list of all certified emissions testing stations on its website. You can search by ZIP code or county to find stations close to your home or workplace. The list shows each station's address, phone number, and hours of operation.
You can also call the IEPA's emissions hotline at 1-800-253-5747 to ask for station locations in your area. The staff can tell you which stations are currently open and may have shorter wait times. Some stations take appointments; others operate on a walk-in basis. Calling ahead saves you a trip if a station is temporarily closed or has a long backlog.
What happens during the test
When you arrive at the station, bring your vehicle registration and a photo ID. The technician will hook your vehicle to a machine that reads emissions data from your engine's onboard diagnostic system. For most vehicles made after 1996, this is a computer-to-computer connection that takes just a few minutes.
For older vehicles or those with certain issues, the technician may perform a tailpipe test, where a probe measures the actual gases coming from your exhaust. This takes a bit longer but follows the same basic process. The technician will not drive your vehicle or take it off the property — the test happens while your car is parked and running.
Once the test is complete, you will receive a printed receipt showing whether you passed or failed. If you pass, the station sends the results electronically to the IEPA, and your registration can be renewed. You do not need to do anything else.
What to do if you fail the emissions test
If your vehicle fails, the receipt will show which emissions standards it did not meet. Common reasons for failure include a faulty oxygen sensor, a loose gas cap, a malfunctioning catalytic converter, or problems with the fuel injection system. The receipt may also include a code that a repair shop can use to diagnose the issue.
You have 30 days from the test date to fix the problem and return to the same station for a retest at no additional charge. If you go to a different station, you will have to pay the testing fee again. During those 30 days, you can still drive your vehicle — a failed emissions test does not when ready suspend your registration, though you cannot renew it until you pass.
If you are unsure what is wrong with your vehicle, take the receipt to a repair shop and ask them to diagnose the issue using the code provided. Many shops can identify and fix common emissions problems for $100 to $500, though costs vary widely depending on what needs repair. Some stations also offer repair services on-site.
Emissions testing in Cook County versus the rest of Illinois
Cook County, which includes Chicago and surrounding suburbs, has stricter emissions requirements than the rest of the state. Vehicles registered in Cook County must be tested every year instead of every two years. The testing procedure is the same, but the annual requirement means you need to plan for more frequent visits to a testing station.
If you move from Cook County to another part of Illinois, or vice versa, your testing schedule changes based on your new registration address. When you update your registration with the Secretary of State, make sure your address is correct so you receive the right renewal notice with the correct testing important date.
Vehicles that are exempt from emissions testing
Not every vehicle in Illinois needs an emissions test. Vehicles that are less than four model years old are exempt — so a vehicle purchased in 2023 would not need testing until 2027. Vehicles over 25 model years old are also exempt, as are motorcycles, trailers, and vehicles registered as historic or antique.
Diesel vehicles have different testing requirements than gasoline vehicles and are tested at separate stations. If you own a diesel vehicle, ask the IEPA hotline which stations near you perform diesel testing, as not all certified stations do.
If your vehicle is exempt, you still need to renew your registration, but you do not need to submit an emissions test result. Your registration renewal notice will tell you whether your vehicle requires testing.
How to renew your registration after passing the test
Once you pass the emissions test, the station sends the results to the IEPA electronically. You do not need to print or mail anything. When you renew your vehicle registration through the Secretary of State's office — either online, by mail, or in person — the system will show that you have passed the test.
You can renew your registration online through the Illinois Secretary of State website, by mail, or at a local driver services facility. If you renew online or by mail, the process is the same whether you just passed an emissions test or are exempt. You will need your current registration card and a valid payment method.
If you fail the test and do not retest within 30 days, your registration renewal will be blocked until you pass. The Secretary of State's system will not allow you to complete the renewal until the IEPA confirms a passing test result.
Frequently Asked Questions
Can I test my vehicle before my registration expires?
Yes. You can take the emissions test up to 120 days before your registration expires. This gives you time to fix any problems and retest if needed, without rushing to meet your renewal important date. The test result is valid for the full two-year (or one-year in Cook County) registration period.
What if I just bought a used car and do not know when it was last tested?
Check your registration renewal notice — it will show your testing important date. If you do not have a notice, call the Secretary of State at 1-217-782-6900 or check your registration status online. You can also ask the previous owner when the car was last tested, though you are not required to accept their word for it.
Do I need to make an appointment or can I just show up?
It depends on the station. Some stations take appointments and others operate walk-in only. Call ahead or check the station's website to find out. During busy times like the end of the month, wait times can be long, so an appointment may save you time.
What if I move out of Illinois before my test is due?
You do not need to take an Illinois emissions test if you move out of state before your important date. However, you must still renew or surrender your Illinois registration. If you plan to move, contact the Secretary of State to update your address or cancel your registration so you do not receive renewal notices.
Can I test a vehicle I am selling or buying?
A vehicle must be registered in your name to be tested. If you are buying a used car, the seller should provide proof that the vehicle passed its most recent emissions test. If the test is expired or failed, the new owner will need to pass a test before renewing the registration in their name.